A method for using high intensity focused ultrasound (HIFU) to treat neurological structures to achieve a desired therapeutic effect. Depending on the dosage of HIFU applied, it can have a reversible or irreversible effect on neural structures. For example, a relatively high dose of HIFU can be used to permanently block nerve function, to provide a non-invasive alternative to severing a nerve to treat severe spasticity. Relatively lower doses of HIFU can be used to reversibly block nerve function, to alleviate pain, to achieve an anesthetic effect, or to achieve a cosmetic effect. Where sensory nerves are not necessary for voluntary function, but are involved in pain associated with tumors or bone cancer, HIFU can be used to non-invasively destroy such sensory nerves to alleviate pain without drugs. Preferably, ultrasound imaging synchronized to the HIFU therapy is used to provide real-time ultrasound image guided HIFU therapy of neural structures.